Pixel group and column token display architectures

ABSTRACT

A flat-panel display comprises a display substrate, an array of pixels distributed in rows and columns over the display substrate, the array having a column-control side, and column controller disposed on the column-control side of the array providing column data to the array of pixels through column-data lines. In some embodiments, rows of pixels in the array of pixels form row groups and each column of pixels in a row group receives column data through a separate column-data line. In some embodiments, each pixel in each column of pixels in the array of pixels is serially connected and each pixel in the array of pixels comprises a token-passing circuit for passing a token through the serially connected column of pixels.

CROSS REFERENCE TO RELATED APPLICATIONS

Reference is made to U.S. Pat. No. 9,930,277, filed Jan. 21, 2016,entitled Serial Row-Select Matrix Addressed System by Cok and to U.S.Pat. No. 10,360,846 filed May 9, 2017, entitled Distributed Pulse-WidthModulation System with Multi-Bit Digital Storage and Output Device byCok et al., the disclosures of which are incorporated herein byreference in their entirety.

FIELD OF THE DISCLOSURE

The present disclosure relates to active-matrix display architectureshaving row and column control signals.

BACKGROUND OF THE DISCLOSURE

Flat-panel displays are widely used in conjunction with computingdevices, in portable electronic devices, and for entertainment devicessuch as televisions. Such displays typically employ an array of pixelsdistributed over a display substrate to display images, graphics, ortext. In a color display, each pixel includes light emitters that emitlight of different colors, such as red, green, and blue. For example,liquid crystal displays (LCDs) employ liquid crystals to block ortransmit light from a backlight behind the liquid crystals and organiclight-emitting diode (OLED) displays rely on passing current through alayer of organic material that glows in response to the current.Displays using inorganic light-emitting diodes (LEDs) as pixel elementsare also in widespread use for outdoor signage and have beendemonstrated in a 55-inch television.

Displays are typically controlled with either a passive-matrix (PM)control scheme employing electronic control circuitry external to thepixel array or an active-matrix (AM) control scheme employing electroniccontrol circuitry in the pixels on the display substrate and associatedwith each light-emitting element. Both OLED displays and LCDs usingpassive-matrix control and active-matrix control are available. Anexample of such an AM OLED display device is disclosed in U.S. Pat. No.5,550,066. In a PM-controlled display, each pixel in a row is stimulatedto emit light at the same time while the other rows do not emit lightand each row is sequentially activated at a high rate to provide theillusion that all of the rows simultaneously emit light. In contrast, inan AM-controlled display, data is concurrently provided to and stored inpixels in a row and the rows are sequentially activated to load the datain the activated row. Each pixel emits light corresponding to the storeddata when pixels in other rows receive data so that all of the rows ofpixels in the display emit light at the same time, except possibly therow loading pixels. In such AM systems, the row activation rate can bemuch slower than in PM systems, for example divided by the number ofrows. Nonetheless, for AM displays, such as HD, 4 k, or 8 k displayswith a large number of rows, the rate at which data must be loaded intosuccessive rows can be greater than desired over relatively largedisplay substrates, for example greater than one, two, or three meters,so that power, ground, and signal distribution can degrade, leading todifficulties in proper pixel control.

Active-matrix circuits are commonly constructed with thin-filmtransistors (TFTs) in a semiconductor layer formed over a displaysubstrate and employing a separate TFT circuit to control eachlight-emitting pixel in the display. The semiconductor layer istypically amorphous silicon or poly-crystalline silicon and isdistributed over the entire flat-panel display substrate. Thesemiconductor layer is photolithographically processed to formelectronic control elements, such as transistors and capacitors.Additional layers, for example insulating dielectric layers andconductive metal layers are provided, often by evaporation orsputtering, and photolithographically patterned to form electricalinterconnections, or wires. In some implementations, small integratedcircuits (ICs) with a separate IC substrate disposed on a displaysubstrate control pixels in an AM display. The integrated circuits canbe disposed on the display substrate using micro-transfer printing, forexample as taught in U.S. Pat. No. 9,930,277 referenced above.

Typically, each display sub-pixel is controlled by one control element,and each control element includes at least one transistor. For example,in a simple active-matrix organic light-emitting diode (OLED) display,each control element includes two transistors (a select transistor and apower transistor) and one capacitor for storing a charge specifying theluminance of the sub-pixel. Each OLED element employs an independentcontrol electrode connected to the power transistor and a commonelectrode. In contrast, an LCD typically uses a single transistor tocontrol each pixel. Control of the light-emitting elements is usuallyprovided through a data signal line (column-data line), a select signalline (row-select line), a power connection, and a ground connection.Active-matrix elements are not necessarily limited to displays and canbe distributed over a substrate and employed in other applicationsrequiring spatially distributed control.

There remains a need for active-matrix display systems that provideimproved signal distribution over relatively large display substrates.

SUMMARY

The present disclosure includes, among various embodiments, a flat-paneldisplay comprising a display substrate, an array of pixels distributedin rows and columns over the display substrate, the array having acolumn-control side, and a column controller disposed on thecolumn-control side of the array operable to provide column data to thepixels in the array of pixels through column-data lines. (Column-datalines can be wires or traces on the display substrate, for example metalwires.) Rows of pixels in the array of pixels are arranged in rowgroups. For each row group of the row groups, each column of pixels inthe row group receives column data from the column controller through aseparate one of the column-data lines, and no pixel of the array ofpixels in any other row group receives column data through the separateone of the column-data lines. Thus, the pixels in each row group receivecolumn data through different column-data lines than pixels in any otherrow group. Columns of pixels in each row group receive common columndata.

The number of row groups can be equal to two or greater than two, forexample three, four, five, eight, ten, twelve, or sixteen. In someembodiments, the row groups can be spatially adjacent over the displaysubstrate. In some embodiments, the rows in the row groups are spatiallyinterdigitated over the display substrate.

Each pixel can comprise one or more inorganicmicro-light-emitting-diodes. Each inorganic micro-light-emitting-diodescan have a length and width no greater than 200 microns, no greater than100 microns, no greater than 50 microns, no greater than 20 microns, nogreater than 10 microns, no greater than 5 microns, or no greater than 3microns.

Some embodiments of the present disclosure comprise a row controlleroperable to provide row-select signals through row-select lines to rowsof pixels in each of the row groups in the array of pixels. (Row-selectlines can be wires or traces on the display substrate, for example metalwires.) Each row-select line can be electrically separate andindependently controlled by the row controller from every other of therow-select lines. Row-select lines in different ones of the row groupscan be electrically connected and commonly controlled by the rowcontroller or rows of pixels in different row groups can alternate overthe display substrate so that rows of pixels in different ones of therow groups are interdigitated and commonly connected. The row controllercan comprise row-control circuits that are serially connected, forexample in a daisy chain. Each row-control circuit can comprise atoken-passing circuit for passing a row-select token through theserially connected row-control circuits. The row controller can providetiming signals to the pixels. The row controller can comprise a singleintegrated circuit or multiple, electrically connected integratedcircuits.

In some embodiments, each pixel comprises a pixel timing circuit. Thetiming circuits in each pixel can operate independently of the timingcircuits in other pixels and can each generate time-dependent controlsignals for controlling the brightness of the light emitters in thepixel. Inorganic micro-light-emitting diodes can efficiently operate ata desired current density and can therefore operate efficiently at aconstant current where pixel brightness is controlled by controlling thelength of time that the inorganic micro-light-emitting diodes areoperating (e.g., operated in a pulse width modulation mode).

According to some embodiments of the present disclosure, for each columnof the pixels in each of the row groups, each pixel in the column isserially connected (e.g., with wires or traces comprising metal or otherelectrical conductors such as a transparent conductive oxide ornanowires) and each pixel in the array of pixels comprises atoken-passing circuit for passing a row-select token through each columnof serially connected pixels in each of the row groups. In someembodiments, the rows form a single row group and the column controllerprovides a row-select token to a single row of pixels, the pixels ineach column can be serially connected, and each pixel in the array ofpixels can comprise a token-passing circuit for passing a row-selecttoken through the serially connected column of pixels. In someembodiments, the rows are divided into multiple row groups, the columncontroller provides a row-select token to at least one row of pixels ineach of the row groups of the multiple row groups, the pixels in eachcolumn in each row group can be serially connected, and each pixel inthe array of pixels can comprise a token-passing circuit for passing arow-select token through the serially connected column of pixels in eachrow group. In some embodiments, the rows are divided into multiple rowgroups, the column controller can provide a row-select token to at leastone (e.g., one) row of pixels in only one of the row groups of themultiple row groups, the pixels in each column in each row group can beserially connected, the row groups are serially connected (e.g., pixelsin different row groups are serially connected with serial connections),and each pixel in the array of pixels can comprise a token-passingcircuit for passing a row-select token through the serially connectedcolumn of pixels in each row group.

According to some embodiments, wires (for example column-data lines andserial connection lines) occupy no less than 5%, no less than 10%, noless than 20%, no less than 50%, no less than 60%, no less than 70%, noless than 80%, or no less than 90% of the area between the columns ofpixels in a display area defined by a convex hull of the pixels 20 on asurface of the display substrate on which the pixels are disposed.Pixels can be disposed between wires on the display substrate in thedisplay area and not over or under wires on the display substrate in thedisplay area.

According to some embodiments of the present disclosure, each of thecolumns of pixels in the array of pixels comprises pixels in two or moredifferent ones of the row groups. Each column of pixels in the array ofpixels can comprise pixels that are electrically connected to differentones of the column-data lines.

According to some embodiments of the present disclosure, a flat-paneldisplay comprises a display substrate, an array of pixels distributed inrows and columns over the display substrate, and a column controlleroperable to provide column data to the pixels in the array throughcolumn-data lines. The rows of pixels in the array of pixels arearranged in row groups and each of the column-data lines electricallyconnects to only one column of pixels in one of the row groups (e.g.,the pixels in one column of one of the row groups). Each of the columnsof pixels in the array of pixels can comprise pixels in two or moredifferent ones of the row groups. Each column of pixels in the array cancomprise pixels that are electrically connected to different ones of thecolumn-data lines. The rows of pixels in the array can be electricallyconnected to a row controller operable to provide row-select signals tothe rows of pixels.

According to some embodiments, for each column of the columns of pixelsin the array, the column of pixels comprises two or more subsets ofpixels and, for each subset of the two or more subsets of pixels, onlythe pixels in the subset are electrically connected to a separate one ofthe column-data lines. The pixels in each of the rows of pixels in thearray can be electrically connected with a corresponding row-selectline.

According to some embodiments, for each row of the rows of pixels in thearray, each pixel in the row is in a column of the array, each pixel inthe row is electrically connected to a separate one of the column-datalines, and the separate column-data line is electrically connected toless than all of the pixels in the column of the array.

According to some embodiments of the present disclosure, a displaycomprises an array of pixels distributed in M rows and N columns, thearray having a column-control side. Rows of pixels in the array ofpixels form G row groups, G greater than one, and a column controllerdisposed on the column-control side of the array is operable to providecolumn data to the array of pixels through N×G separate column-datalines.

According to some embodiments of the present disclosure, a method ofcontrolling a flat-panel display comprises providing, by a columncontroller, first column data on a first column-data line to firstpixels in a column of an array of pixels that are in a first row group;and providing, by the column controller, second column data on a secondcolumn-data line to second pixels in the column of the array of pixelsthat are in a second row group. The first column-data line and thesecond column-data line are different column-data lines and the firstcolumn data and the second column data are provided concurrently and atthe same time and can provide different column data. In someembodiments, the first column of pixels in the first row group and thesecond column of pixels in the second row group are in a common columnof the array of pixels. Some embodiments comprise providing a row-selecttoken to a row of pixels in each of the first row group and the secondrow group by the column controller. Some embodiments comprise providinga row-select token to a single row of pixels in the array of pixels bythe column controller and row-select tokens are provided from one row ofpixel in a row group to another row of pixels in a different row group,for example through serial connection lines (wires).

According to embodiments of the present disclosure, a flat-panel displaycomprises a display substrate, an array of pixels distributed in rowsand columns over the display substrate, and a column controller disposedover the display substrate is operable to provide data to the array ofpixels through column-data lines. Each pixel in each column of pixels inthe array of pixels is serially connected and each pixel in the array ofpixels comprises a token-passing circuit for passing a row-select tokenthrough the serially connected column of pixels.

Each of the pixels can comprise one or more inorganicmicro-light-emitting-diodes (LEDs), for example red-light-emitting redLEDs, green-light-emitting green LEDs, and blue-light-emitting blueLEDs. Each of the inorganic micro-light-emitting-diodes can have alength and width no greater than 200 microns, no greater than 100microns, no greater than 50 microns, no greater than 20 microns, or nogreater than 100 microns. Such small LEDs leave space on the displaysubstrate for additional column-data lines and serial connections.

The column controller can be operable to provide a row-select token tothe pixels in a row of the array of pixels. Rows of pixels can bearranged in row groups. Each pixel in each column of row groups can beserially connected. Each column of pixels in a row group can receivecolumn data through a separate column-data line. In some embodiments, noother pixel of the array of pixels in any other row group receivescolumn data through the separate one of the column-data lines. Thus,pixels in different row groups receive column data from the columncontroller through different column-data lines. The number of row groupscan be greater than two. The column controller can provide a token(e.g., a row-select token) to the pixels in at least one (e.g., one) rowof each of the row groups. The row-select token can be provided to a rowof every row group at the same time or can be provided to a row of onlyone of the row groups and the row-select token can be passedsequentially from row group to row group.

Rows of pixels in different ones of the row groups can beinterdigitated.

According to some embodiments, the array of pixels has a column-controlside and the column controller is disposed on the column-control side ofthe array. Wires, for example column-data lines can occupy no less than5%, 10%, 20%, 50%, 60% 70%, 80%, or 90% of the area between at least aportion of the columns of pixels on a surface of display substrate onwhich the pixels are disposed, for example between columns of pixels inthe display are of the display substrate.

Each of the pixels can comprise a pixel timing circuit that controls thepixel or that controls the amount of time a light-emitting in the pixelemits light, for example at a constant current. The pixel timing circuitin each pixel can be separate and operate independently of the pixeltiming circuit in any other pixel. The pixel timing circuit can be adigital circuit providing pulse width modulation control or an analogcircuit comprising one or more charge-storage capacitors.

According to embodiments of the present disclosure, a method ofcontrolling a flat-panel display comprises providing a display andproviding a row-select token to a row of pixels in the array of pixelsby the column controller. In some embodiments, methods of the presentdisclosure comprise providing a row-select token to a row of pixels ineach row group by the column controller. In some embodiments, methods ofthe present disclosure comprise providing a row-select token to one rowof pixels in one row group by the column controller.

According to embodiments of the present disclosure, a flat-panel displaycomprises an array of pixels distributed in rows and columns and acolumn controller operable to provide data to the array of pixels andexclusively controlling the array of pixels (e.g., by providingrow-select tokens through serial connections) so that no row controlleris needed or used to control the flat-panel display. The array of pixelscan have a column-control side and the column controller can be disposedon the column-control side of the array. In some embodiments, flat-paneldisplay control circuits on the display substrate outside of the displayarea are disposed only on the column-control side.

Each of the pixels can comprise one or more inorganicmicro-light-emitting-diodes, for example three LEDs in a color pixel.Each of the inorganic micro-light-emitting-diodes can have a length anda width each no greater than 200 microns, no greater than 100 microns,no greater than 50 microns, no greater than 20 microns, no greater than215 microns, or no greater than 10 microns and each of the pixels cancomprise a pixel timing circuit.

Embodiments of the present disclosure provide active and passive displaycontrol methods and architectures that enable improved control oflarge-substrate displays with a large number of pixels usinglower-frequency signals and fewer control lines.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, aspects, features, and advantages ofthe present disclosure will become more apparent and better understoodby referring to the following description taken in conjunction with theaccompanying drawings, in which:

FIG. 1 is a schematic plan view of a display having two row groupsaccording to illustrative embodiments of the present disclosure;

FIG. 2 is a schematic circuit diagram and details of a pixel accordingto illustrative embodiments of the present disclosure;

FIG. 3 is a schematic plan view of a display having two interdigitatedrow groups according to illustrative embodiments of the presentdisclosure;

FIG. 4 is a schematic of a row controller according to illustrativeembodiments of the present disclosure;

FIG. 5 is a schematic plan view of a display having four row groupsaccording to illustrative embodiments of the present disclosure;

FIG. 6 is a schematic plan view of a display having four interdigitatedrow groups according to illustrative embodiments of the presentdisclosure;

FIG. 7 is a simplified schematic of a pixel controller according toillustrative embodiments of the present disclosure;

FIG. 8 is a schematic plan view of a display having serial connectionsaccording to illustrative embodiments of the present disclosure;

FIG. 9 is a simplified schematic of a pixel controller according toillustrative embodiments of the present disclosure;

FIG. 10 is a schematic plan view of a display having two row groups andserial connections according to illustrative embodiments of the presentdisclosure;

FIG. 11 is a schematic plan view of a display having two row groups andserial connections between row groups according to illustrativeembodiments of the present disclosure;

FIG. 12 is a schematic plan view of a display having four row groups andserial connections according to illustrative embodiments of the presentdisclosure;

FIG. 13 is a schematic plan view of a display having wires betweenpixels in a display area and according to illustrative embodiments ofthe present disclosure; and

FIGS. 14-19 are flow diagrams of methods according to illustrativeembodiments of the present disclosure.

Features and advantages of the present disclosure will become moreapparent from the detailed description set forth below when taken inconjunction with the drawings, in which like reference charactersidentify corresponding elements throughout. In the drawings, likereference numbers generally indicate identical, functionally similar,and/or structurally similar elements. The figures are not drawn to scalesince the variation in size of various elements in the Figures is toogreat to permit depiction to scale.

DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS

Embodiments of the present disclosure provide, inter alia, active- andpassive-matrix display control methods and architectures that enableimproved control of flat-panel displays (e.g., large-substrate displays)using lower-frequency signals and fewer control lines of greater size.The pixels can comprise inorganic light-emitting diodes and the displayscan be analog or digital displays.

According to some embodiments of the present disclosure and asillustrated in FIG. 1, a flat-panel display 99 comprises a displaysubstrate 10, an array 12 of pixels 20 distributed in rows 14 andcolumns 16 over display substrate 10. Array 12 can define a display areaon display substrate 10 and has a column-control side 18. A columncontroller 30 is disposed on column-control side 18 of array 12 andprovides column data to array 12 of pixels 20 through column-data lines32. Each column-data line 32 (e.g., column-data line 32A or column-dataline 32B, collectively column-data lines 32) connects at least a portionof each column 16 of pixels 20 to column controller 30. According tosome embodiments, rows 14 of pixels 20 in array 12 form row groups 44(e.g., row group 44A, row group 44B, collectively row groups 44) andeach column 16 of pixels 20 in a row group 44 receives column datathrough a separate column-data line 32. Column-data lines 32 canindependently and at the same time transmit column data to each column16 of pixels 20 in each row group 44. According to some embodiments, aflat-panel display 99 comprises two or more row groups 44. According tosome embodiments, the number of row groups 44 evenly divides the numberof rows 14 in array 12 of pixels 20. In some embodiments, the number ofrow groups 44 does not evenly divide the number of rows 14 in array 12of pixels 20. According to some embodiments, rows 14 of pixels 20 arecontrolled by a row controller 40 that provides row-control signals(e.g., row-select signals and timing signals) on row-select lines 42 topixels 20. In general, column-data lines 32 can extend in a direction(e.g., vertically or in a y direction) over display substrate 10 androw-select lines 42 can extend in a direction orthogonal to column-datalines 32 (e.g., horizontally or in an x direction). Horizontal andvertical are arbitrary orthogonal directions.

Display substrate 10 can be any useful substrate on which pixels 20 andcolumn-data lines 32 can be suitably disposed, for example glass,plastic, resin, fiberglass, semiconductor, ceramic, quartz, sapphire, orother substrates found in the display or integrated circuit industries.Display substrate 10 can be flexible or rigid and can be substantiallyflat. Column-data lines 32 and row-select lines 42 can be wires (e.g.,photolithographically defined electrical conductors such as metal lines)disposed on display substrate 10 that conduct electrical current fromcolumn controller 30 to columns 16 of pixels 20 and electrical currentfrom row controller 40 to rows 14 of pixels 20.

Column controller 30 can be, for example, an integrated circuit thatprovides control, timing (e.g., clocks) or data signals (e.g.,column-data signals) through column-data lines 32 to columns 16 ofpixels 20 to enable pixels 20 to control light in flat-panel display 99.Each column-data line 32 can be electrically separate and optionallyindependently controlled from every other column-data line 32 by columncontroller 30. Column controller 30 can be disposed completely andexclusively on column-control side 18 (e.g., as shown in FIG. 1). Columncontroller 30 can comprise a single integrated circuit or can comprisemultiple integrated circuits, e.g., electrically connected integratedcircuits. The integrated circuit(s) can be micro-transfer printed asunpackaged dies and can comprise fractured or separated tether(s).

Row controller 40 can be, for example, an integrated circuit thatprovides control signals (e.g., row-select signals) and/or timingsignals (e.g., clocks or timing signals such as pulse-width modulation(PWM) signals) through row-select lines 42 to rows 14 of pixels 20 tocause pixels 20 to control light in flat-panel display 99. Eachrow-select line 42 can be electrically separate and optionallyindependently controlled from every other row-select line 42 by rowcontroller 40. Row controller 40 can be disposed completely andexclusively on a side of display substrate 10 adjacent to column-controlside 18 (e.g., as shown in FIG. 1). Row controller 40 can comprise asingle integrated circuit or can comprise multiple integrated circuits,e.g., electrically connected integrated circuits. The integratedcircuit(s) can be micro-transfer printed as unpackaged dies and cancomprise fractured or separated tether(s).

Array 12 of pixels 20 can be a completely regular array 12 (e.g., asshown in FIG. 1) or can have rows 14 or columns 16 of pixels 20 that areoffset from each other, so that rows 14 or columns 16 of pixels 20 arenot disposed in a straight line and can, for example, form a zigzag line(not shown in the Figures) or, as another example, have non-uniformspacing(s).

Pixels 20 can be active- or passive-matrix pixels 20, can be analog ordigital, and comprise one or more light-controlling elements, forexample light emitter(s) such as light-emitting diode(s) 50 (LED(s) 50).Pixels 20 can comprise light-emitting diodes 50, e.g., inorganiclight-emitting diodes 50 such as horizontal inorganic light-emittingdiodes 50 (e.g., as shown in the detail of FIG. 2) or vertical inorganiclight-emitting diodes 50 (not shown in the Figures). Inorganiclight-emitting diodes 50 can have a small area, for example having alength and a width each no greater than 20 microns, no greater than 50microns, no greater than 100 microns, or no greater than 200 microns.Such small light emitters leave additional area on display substrate formore or larger wires, e.g., additional column-data lines 32, serialconnections 60, or ground and power wires.

As shown in more detail in FIG. 2, in certain active-matrix embodimentsof the present disclosure, pixels 20 can comprise a pixel controller 24.Pixels 20 can comprise a red light-emitting diode 52 that emits redlight, a green light-emitting diode 54 that emits green light, and ablue light-emitting diode 56 that emits blue light (collectivelylight-emitting diodes 50 or LEDs 50) under the control of pixelcontroller 24. In certain embodiments, light emitters that emit light ofother color(s) are included in pixel 20, such as a yellow light-emittingdiode. Light-emitting diodes 50 can be mini-LEDs (e.g., having a largestdimension no greater than 500 microns) or micro-LEDs (e.g., having alargest dimension of less than 100 microns). Pixels 20 can emit onecolor of light or white light (e.g., as in a black-and-white display) ormultiple colors of light (e.g., red, green, and blue light as in a colordisplay). Pixels 20 can comprise multiple elements (e.g., pixelcontroller 24 and LEDs 50) disposed and electrically connected directlyon display substrate 10 or can comprise multiple elements disposed andelectrically connected on a pixel substrate 22 separate and independentfrom display substrate 10 with pixel substrate 22 disposed on displaysubstrate 10. Any one or more of pixel controller 24 and LEDs 50 can bemicro-transfer printed onto display substrate 10 or onto pixel substrate22. If pixel controller 24 and LEDs 50 are disposed on separate andindependent pixel substrate 22 to form pixel 20, pixel 20 (with pixelsubstrate 22) can be micro-transfer printed from a pixel sourcesubstrate onto display substrate 10 and electrically connected tocontrol signal wires (e.g., row-control, column-data, power, and groundsignal wires) on display substrate 10. Micro-transfer printed devices orstructures (e.g., LEDs 50, pixel controller 24, or pixel 20) cancomprise fractured or separated tether(s) as a consequence ofmicro-transfer printing from a source to a target substrate.

According to some embodiments of the present disclosure, anactive-matrix pixel controller 24 receives column-data signals fromcolumn controller 30 through column-data line 32 and row-select signalsfrom row controller 40 through row-select line 42. When a pixel 20 isselected by row-select line 42 (e.g., controlled by pixel controller 24AND gate), data received from column-data line 32 is stored in pixelmemory 26 and, using a pixel timing circuit 28, controls light-emittingdiodes 50 to emit light. (Pixel controller 24 as illustrated in thedetail of FIG. 2 is a simplified schematic and does not include all ofthe logic circuits necessary to actually implement the desiredfunctionality. U.S. Patent Publication No. 2018/019747 describescircuits useful in such application and its contents are entirelyincorporated by reference herein.) Pixel memory 26 can be a digitalmemory (e.g., an SRAM or shift register storing digital valuesrepresenting the desired brightness of each light-emitting diode 50) oran analog memory (e.g., one or more capacitors storing a chargerepresenting the desired brightness of each light-emitting diode 50).Pixel controllers 24 can be thin-film circuits. According to someembodiments of the present disclosure, pixel controllers 24 compriseintegrated circuits formed in a crystalline semiconductor (e.g.,silicon) substrate that are transferred from a native source wafer tonon-native display substrate 10 or to a non-native pixel substrate 22,for example by micro-transfer printing. As a consequence ofmicro-transfer printing, pixel controller 24 can comprise a fractured orseparated controller tether. Such crystalline circuits have much betterperformance and a smaller size than thin-film semiconductor circuits.The smaller size of pixel controller 24 provides additional area overdisplay substrate 10 for additional or larger column-data lines 32 orserial connections 60, enabling embodiments of the present disclosure.

According to some embodiments of the present disclosure and as shown inthe detail of FIG. 2, pixels 20 comprise inorganic micro-light-emittingdiodes 50 that have a length L and a width over display substrate 10 orpixel substrate 22 that is no greater than 100 microns (e.g., no greaterthan 50 microns, no greater than 20 microns, no greater than 15 microns,no greater than 12 microns, no greater than 10 microns, no greater than8 microns, no greater than 5 microns, or no greater than 3 microns).Such relatively small light emitters disposed on a relatively largedisplay substrate 10 (for example a laptop display, a monitor display,or a television display) take up relatively little area on displaysubstrate 10 so that the fill factor of LEDs 50 on display substrate 10(e.g., the aperture ratio or the ratio of the sum of the areas of LEDs50 over display substrate 10 to the convex hull area of displaysubstrate 10 that includes LEDs 50 or minimum rectangular area of pixel20 array 12) is no greater than 30% (e.g., no greater than 20%, nogreater than 10%, no greater than 5%, no greater than 1%, no greaterthan 0.5%, no greater than 0.1%, no greater than 0.05%, or no greaterthan 0.01%). For example, an 8K display (having a display array 12bounding 8192 by 4096 display pixels 20) over a 2-meter diagonal 9:16display with micro-LEDs 50 having a 15-micron length and 8-micron widthhas a fill factor of much less than 1%. An 8K display having 40 micronby 40 micron pixels 20 can have a fill factor of about 3%. According toembodiments of the present disclosure, because the display area fillfactor of the micro-LEDs 50 can be so small, timing and row selectfunctions can be integrated into pixels 20 in the display area ratherthan integrated into circuits external to the display area (e.g., intorow controller 40) so that wiring in the display area is reduced (e.g.,in number) and/or individual wire size can be increased (e.g., withoutneeding to increase the number of wiring layers) and display and pixelcontrol is simplified. Circuits and structures of this size suitable forembodiments of the present disclosure have been designed andconstructed. As discussed in U.S. Pat. No. 9,991,163, whose contents areincorporated by reference herein, a display substrate 10 having such asmall fill factor can use the remaining area of display substrate 10 toprovide other functionality.

According to some embodiments of the present disclosure, the remainingarea not occupied by pixels 20 is used at least partly to provideadditional column-data lines 32 to separately control or communicatewith row groups 44 of pixel 20 rows 14. By separately controlling orcommunicating with separate row groups 44, pixels 20 in different rowgroups 44 can receive signals (for example data) at the same time,reducing the communication frequency necessary and increasing the timeavailable to send the control or data signals from column controller 30to pixels 20. Lower-frequency signals can be transmitted over largerareas with an improved signal-to-noise ratio and are therefore morereliable and robust. Moreover, the remaining area can also be used toform larger or wider column-data lines 32 having reduced resistance.Thus, according to some embodiments of the present disclosure, largerflat-panel displays 99 can be controlled more easily with fewercommunication errors and improved power and ground distribution and withfewer integrated circuits.

In contrast to embodiments of the present disclosure, existing prior-artflat-panel displays have a desirably large fill factor. For example, thelifetime of OLED displays is increased with a larger fill factor becausesuch a larger fill factor reduces current density and improves organicmaterial lifetimes. Similarly, liquid-crystal displays (LCDs) have adesirably large fill factor to reduce the necessary brightness of thebacklight (because larger pixels transmit more light), improving thebacklight lifetime and display power efficiency. Thus, prior displayscannot reduce control frequency and improve control line conductivitybecause there is no space on their display substrates for additional orlarger control lines, in contrast to embodiments of the presentdisclosure. In some embodiments of the present disclosure, any two ormore of pixels 20, column-data lines 32, and row-select lines 42 aredisposed in a common layer on display substrate 10 and pixels 20 arenot, for example, disposed over or below column-data lines 32 androw-select lines 42. Display substrate 10 costs are reduced by disposingany two or more of pixels 20, column-data lines 32, and row-select lines42 in a common layer.

As shown in the embodiments of FIG. 1, in some embodiments, rows 14 ofpixels 20 in array 12 are arranged in two row groups 44, row group 44Aand row group 44B. (More row groups 44 can be used, for example, forlarger or higher definition displays.) Each of row group 44A and rowgroup 44B are individually and independently connected by a differentset of column-data lines 32 (e.g., column-data lines 32A and column-datalines 32B, respectively) to column controller 30. Different pixels 20 indifferent row groups 44 in the same column 16 are connected to differentcolumn-data lines 32, as can be seen in each of the columns 16 of pixels20 in FIG. 1 (where the top four pixels 20 of each column 16 areconnected to a separate column-data line 32A from column-data line 32Bthat connects the bottom four pixels 20 in the column 16). Thus, columncontroller 30 can provide column-data signals at the same time to pixels20 in different row groups 44. At the same time, row controller 40 canprovide corresponding row-select signals to rows 14 in the different rowgroups 44 at the same time. For example, FIG. 1 illustrates an eight byeight array 12 of pixels 20 arranged in eight rows 14 and eight columns16. The eight rows 14 of pixels 20 are divided into two row groups 44Aand 44B. Row controller 40 can select pixels 20 in first (top) row 14(in row group 44A) and pixels 20 in fifth row 14 (in row group 44B) atthe same time. Correspondingly, column controller 30 provides columndata to each column in row group 44A and row group 44B at the same timeon column-data lines 32A and 32B, respectively, so that pixels 20 infirst row 14 in row group 44A are selected to receive data oncolumn-data lines 32A at the same time as pixels 20 in fifth row 14 inrow group 44B receive data on column-data lines 32B. Because differentcolumn-data lines 32 (e.g., column-data lines 32A and column-data lines32B) are connected to rows 14 of pixels 20 in different row groups 44,pixels 20 in first row 14 (in row group 44A) can receive differentcolumn data from pixels 20 in fifth row 14 (first row 14 in row group44B). Once first and fifth rows 14 of pixels 20 are loaded with data(or, in a passive-matrix embodiment, emit light), pixels 20 in secondrow 14 (in row group 44A) and sixth row 14 (second row 14 in row group44B) can be selected by row controller 40 and provided with column databy column controller 30 through column-data lines 32A and 32B,respectively. The process continues for each subsequent row 14 in eachrow group 44 until all of rows 14 in array 12 are selected and providedwith data. The process then repeats for the next set of column data(e.g., corresponding to an image frame). Because, in some embodiments,as in FIG. 1, two row groups 44A, 44B and two sets of column-data lines32A, 32B are used to control pixels 20, the data rate can be one half ofa conventional display architecture having one row group 44 and one setof column-data lines 32, enabling improved signal integrity.

In some embodiments, and as shown in FIG. 1, row groups 44 are disposedin the top half and the bottom half of flat-panel display 99. In someembodiments, and as illustrated in the schematic plan view of FIG. 3,row-select lines 42 in different row groups 44 are interdigitated andelectrically connected and commonly controlled by row controller 40.Such an arrangement can simplify the layout of display substrate 10 andthe circuits in row controller 40. As shown in FIG. 3, a row 14 ofpixels 20 in row group 44A is electrically connected and controlled incommon with an adjacent row 14 of pixels 20 in row group 44B. Rows 14 ofeach row group 44 alternate over display substrate 10. In someembodiments, more than two row groups 44 are mutually interdigitatedover display substrate 10, for example in an “ABC” interdigitationpattern.

As shown in the embodiments of FIG. 4, row controller 40 can comprisetoken-passing circuits 46 (e.g., flip-flops arranged in a serial shiftregister) that pass a row-select token (e.g., a single bit ofinformation representing a row 14 selection) through token-passingcircuits 46 to control row 14 selection. Each token-passing circuit 46can control a row-select line 42 connected to a row 14 of pixels 20 orto commonly connected rows 14 of pixels 20 in different row groups 44(e.g., as shown in FIG. 4 and corresponding to FIG. 3).

Embodiments of flat-panel display 99 illustrated in FIG. 1 and FIG. 3have two row groups 44. Embodiments illustrated in FIG. 5 have four rowgroups 44, row group 44A, row group 44B, row group 44C and row group 44Delectrically connected to corresponding column-data lines 32A, 32B, 32C,and 32D, respectively, arranged with adjacent row groups 44, as alsoshown in FIG. 1. FIG. 6 illustrates embodiments with rows 14 indifferent row groups 44 alternating so that rows 14 of different rowgroups 44 are interdigitated and are arranged as in FIG. 3. In some suchembodiments, four rows 14 (one in each of row groups 44A, 44B, 44C, 44D)are selected and data provided at the same time on column-data lines32A, 32B, 32C, and 32D, so that the data rate for such a flat-paneldisplay 99 is one quarter of the display rate (frame rate) of aflat-panel display having only one row group. In the extreme case, eachrow 14 can be a different row group 44 and a different column-data line32 is connected to each pixel 20 in each column 16 of pixels 20 in eachrow 14. That is, an M×N array of pixels 23 would have MN column-datalines 32. For example, in an eight by eight array 12 of pixels 20, suchan extreme case would comprise a column-data line 32 for every pixel 20in array 12, totaling 64 column-data lines 32. However, in someembodiments of the present disclosure, a flat-panel display 99 has anumber of row groups 44 less than the number of rows 14 in array 12 sothat some column-data lines 32 are connected to more than one row 14 ofpixels 20 (the more than one row 14 forming a row group 44, e.g., thesome column-data lines 32 are each connected to more than one pixel 20in a common column 16 in the row group 44).

According to some embodiments of the present disclosure and as notedwith respect to FIG. 2, row controller 40 can provide timing signals toeach pixel 20 in a row 14 at the same time. In some such embodiments andas shown conceptually in FIG. 7, pixel timing circuit 28 responds totiming signals 62 (e.g., a clock) to control LEDs 50 in pixel 20 to emitlight. In certain active-matrix embodiments, the magnitude of the lightdesired is stored in pixel memory 26. In certain passive-matrixembodiments, the timing signal itself specifies the pixel brightness.The timing signals (e.g., PWM signals) can be used to control the lengthof time an LED 50 emits light.

According to some embodiments, each pixel 20 can comprise a pixel timingcircuit 28 that internally and independently generates a timing signalcontrolling the brightness of pixel 20, for example in combination withdigital data values stored in pixel memory 26 (for example as describedin U.S. Pat. No. 10,360,846 whose contents are incorporated by referenceherein in their entirety), or as an analog value stored in a capacitor(where pixel memory 26 comprises one or more capacitors, not shown inthe Figures). Such digital pixel timing circuits 28 have been designedand are suitable for embodiments of the present disclosure, for examplehaving an area in an active-matrix pixel 20 small enough to fitalongside the other elements of flat-panel display 99. In some suchembodiments, internally generated timing signals need not be provided byrow controller 40 or column controller 30, simplifying the row controlcircuitry (e.g., row controller 42) and reducing the bandwidth andfrequency requirements for row-select signals on row-select lines 42 orcolumn-data signals on column-data lines 32, as certain operations caninstead be carried out locally at digital pixel timing circuits 28.

In some embodiments and as illustrated in FIG. 7, a pixel controller 24can input column data from column-data line 32 and a row-select signalfrom row-select line 42. If desired, a clock or timing signal 62 can begenerated or recovered from the row-select signal or column-data signalswith a clock recovery circuit 64. When a row 14 is selected, therow-select signal on row-select line 42 can be combined with thecolumn-data signal (e.g., with an AND gate) to provide data to pixelmemory 26 and timing signal 62 can enable pixel timing circuit 28 tocontrol LEDs 50 in pixel 20 to emit light. (FIG. 7 is a simplifiedschematic intended to illustrate pixel controller 24 and omits circuitrythat may be needed or desired to implement a complete circuit.)

Embodiments illustrated in FIGS. 1-7 comprise a row controller 40.According to some embodiments of the present disclosure and asillustrated in FIG. 8, flat-panel display 99 does not comprise a rowcontroller 40. Functions performed by row controller 40 can be performedby column controller 30 that is appropriately electrically connected topixels 20 and by circuits internal to each pixel 20, e.g., incorporatedinto pixel controller 24. Some such embodiments reduce the amount ofcircuitry needed to control flat-panel display 99 (e.g., circuitry suchas row controller circuitry external to the display area) and reducesthe number of wires (e.g., row-select lines 42) and vias needed tocontrol flat-panel display 99. Thus, embodiments of the presentdisclosure are useful for less complex flat-panel displays having fewerintegrated circuits, fewer wires, and fewer metal layers constructed atreduced expense.

In embodiments illustrated in FIG. 8, each pixel 20 in a column 16 isserially connected through a serial connection 60, e.g., a wire orelectrical conductor that serially connects pixels 20 in a daisy chain,so that each pixel 20 in a row 14 is electrically connected directly toa neighboring pixel 20 in an adjacent row 14. Each pixel 20 comprises atoken-passing circuit 46 in pixel controller 24, for example asillustrated in FIG. 9. A token (e.g., a row-selection control bit) ispassed from column controller 30 into each column 16 of pixels 20 andserially and sequentially propagates from row 14 to the next adjacentrow 14 in the daisy chain through serial connections 60 in response tocontrol and column-data signals provided on column-data lines 32, thussuccessively enabling each row 14 of pixels 20. FIG. 8 shows only onerow group 44, so each row 14 of the entire array 12 is successively andsequentially enabled and receives column data at a time communicatedthrough column-data lines 32. Thus, according to some embodiments of thepresent disclosure, a flat-panel display 99 comprises a displaysubstrate 10, an array 12 of pixels 20 distributed in rows 14 andcolumns 16 over display substrate 10, and a column controller 30disposed over display substrate 10 providing data (e.g., column data orpixel data and control signals) to array 12 of pixels 20 throughcolumn-data lines 32. Each pixel 20 in each column 16 of pixels 20 inarray 12 of pixels 20 can be serially connected independently ofcolumn-data lines 32 and each pixel 20 in array 12 of pixels 20 cancomprise a token-passing circuit 46 for passing a row-select tokenthrough serially connected columns 16 of pixels 20. According to someembodiments, a flat-panel display 99 comprises an array 12 of pixels 20distributed in rows 14 and columns 16 with a column controller 30providing data to array 12 of pixels 20 and exclusively controllingpixels 20 in array 12 so that no row controller 40 is needed. Columncontroller 30 can comprise multiple integrated circuits, for examplemicro-transfer printed micro-integrated-circuits and the multipleintegrated circuits can be serially connected and form, inter alia, aserial shift register. Array 12 of pixels 20 can have a column-controlside 18 and column controller 30 can be disposed on column-control side18 of array 12. Thus, according to some embodiments, flat-panel display99 has no active devices (e.g., a row controller 40 or an integratedcircuit) on any side of flat-panel display 99 except column-control side18, thereby reducing the bezel sizes of those sides. According to someembodiments, a convex hull surrounding and including pixels 20 form adisplay area and flat-panel display 99 includes only wires on displaysubstrate 10 outside of the display area, except on column-control side18 of display substrate 10. In some embodiments, the number of controlor data wires (e.g., column-data lines 32) on a side of array 12 otherthan column-control side 18 is equal to the number of row groups 44.

FIG. 9 is a simplified schematic illustrating embodiments of pixelcontroller 24 in pixel 20 useful for flat-panel displays 99, for exampleas illustrated in FIG. 8. Pixel controller 24 is responsive tocolumn-data line 32 to generate a timing signal 62 with a clock recoverycircuit 64. Timing signal 62 controls token-passing circuit 46 (e.g.,comprising a flip-flop that, in combination with other pixels 20 in acommon column 16, forms a serial shift register). Token-passing circuit46 can also generate a row-select signal that enables pixel memory 26 tostore column data. In response to stored column data (specifying thedesired brightness of LEDs 50), pixel timing circuit 28 controls LEDs 50to emit light, for example using internally generated PWM and binarylogarithmic signals or delta sigma signals to control the time for whicha constant current is provided to LEDs 50. The use of PWM enables aconstant current control of LEDs 50, improving their efficiency. Inanalog embodiments, pixel memory 26 can comprise capacitors thatdischarge current through LEDs 50 so that pixel timing circuit 28 is notneeded.

FIG. 10 illustrates embodiments of the present disclosure comprisingmore than one row group 44. Each of two row groups, 44A and 44B, has aseparate serial connection 60 for row-select token passing so that bothrow group 44A and row group 44B simultaneously receive a row-selecttoken directly from column controller 30. The respective column-datalines 32A and 32B for each of row groups 44A and 44B can thensimultaneously transmit column data and successive rows 14 in each rowgroup 44 are sequentially selected to receive their respective columndata. Thus, in some such embodiments, each pixel 20 in each column 16 ofpixels 20 in a row group 44 is serially connected and each pixel 20 inarray 12 of pixels 20 comprises a token-passing circuit 46 for passing arow-select token through serially connected columns 16 of pixels 20 inrow group 44 with serial connection 60. In this configuration, no rowcontroller 40 or row-select lines 42 are needed and the data rate oneach column-data line 32 is one half that of embodiments illustrated inFIG. 8, improving signal-to-noise quality of column data signals oncolumn-data lines 32 and reducing the number of wires and displaycontrol logic.

In embodiments illustrated in FIG. 11, serial connections 60 passrow-select tokens from each row group 44 to the next adjacent row group44 over display substrate 10 so that each row group 44 is initiallysuccessively rather than simultaneously enabled. In some suchembodiments, column controller 30 is directly connected to a row 14 ofpixels 20 in only one row group 44 (e.g., row group 44A), pixels 20 ineach column 16 are serially connected, and each pixel 20 in array 12 ofpixels 20 comprises a token-passing circuit 46 for passing a row-selecttoken through serially connected column 16 of pixels 20. Thus, whenfirst starting up flat-panel display 99, only first row group 44 (e.g.,row group 44A) connected to column controller 30 is enabled, butthereafter each row group 44 (e.g., row group 44B) is successivelyenabled. When first row group 44A passes a row-select token to secondrow group 44B, column controller 30 also passes another row-select tokento first row 14 of first row group 44A, so that rows 14 in both firstand second row groups 44A, 44B are simultaneously enabled, as in FIG.10. Since display frame rates are typically fractions of a second, thestart-up delay needed to successively enable each row group 44 will notbe noticeable to a viewer of flat-panel display 99. Such an arrangementreduces the extent of wires (e.g., serial connections 60) disposed overdisplay substrate 10.

FIG. 12 illustrates embodiments in which array 12 of pixels 20 comprisesfour row groups 44 (e.g., row group 44A, row group 44B, row group 44C,and row group 44D) and each row group 44 is connected to a separate setof column-data lines 32 (e.g., first column-data line 32A is connectedto row group 44A, second column-data line 32B is connected to row group44B, third column-data line 32C is connected to row group 44C, andfourth column-data line 32D is connected to row group 44D). Although notillustrated in FIG. 12, rows 14 of row groups 44 can be interdigitated,for example as shown in FIGS. 3 and 6.

According to some embodiments of the present disclosure, each serialconnection 60 provides a daisy chain connection between pixels 20 in asingle column 16 of a row group 44. If flat-panel display 99 comprises asingle row group 44, as in FIG. 8, a separate and independent serialconnection 60 connects all of pixels 20 in an entire column 16 of array12. No serial connection 60 electrically connects pixels 20 in differentcolumns 16 and each serial connection 60 of each column 16 in each rowgroup 44 is electrically independent of any other serial connection 60,although serial connections 60 can initially be driven by a commonsignal from column controller 30 (e.g., to first row 14 of pixels 20 ina row group 44, as in FIGS. 11 and 12). Although the row-select tokensignals propagated between pixels 20 in separate rows 14 in a row group44 are the same, by electrically separating the row-select token signalsin different columns 16 into separate and independent serial connections60 and by providing a pixel timing circuit 28 in each pixel 20, nocontrol or timing signals (e.g., timing signals 62) extending from onecolumn 16 to another is necessary, in contrast to row-select lines 42controlled by a row controller 42 that extends control or timing signalsto pixels 20 in multiple columns 16 (e.g., as shown in FIG. 1). Thus,less logic and fewer wires need be disposed on display substrate 10 inembodiments in accordance with FIGS. 10-13. In some such embodiments,local timing signals can be independently generated in each pixel 20.

In general, and according to embodiments of the present disclosure, adisplay (e.g., flat-panel display 99) can comprise an array 12 of pixels20 distributed in M rows 14 and N columns 16, array 12 having acolumn-control side 18. Rows 14 of pixels 20 in array 12 of pixels 20form G row groups 44, where G is greater than one. A column controller30 can be disposed on column-control side 18 of array 12 and displaysubstrate 10 providing column data to array 12 of pixels 20 through N×Gseparate column-data lines 32. In embodiments comprising serialconnections 60 between pixels 20 in rows 14, flat-panel display 99 canhave a relatively small bezel on sides other than column-control side 18of array 12 and display substrate 10 and need be connected on only oneside of display substrate 10, reducing the form factor of displaysubstrate 10 and flat-panel display 99. A row controller 40 androw-select lines 42 are unnecessary and the remaining control lines(e.g., column-data lines 32 and serial connections 60) extend in acommon direction over display substrate 10, providing a simpler wirelayout of wider wires having lower resistance and better signalconduction, as well as reduced data rates, providing improved signalintegrity. Such improved signal integrity can be helpful for largedisplays, for example having a diagonal of 0.5 meters to 10 meters,where signals travel over extended wire lengths.

According to some embodiments of the present disclosure and asillustrated in FIG. 13, wires, power lines, ground lines, or signallines (e.g., column-data lines 32) disposed between pixels 20 in rowgroups 44 (e.g., row group 44A, row group 44B) can together occupy asignificant portion of area 80 between columns 16 of pixels 20. Forexample, the wiring can occupy no less than 5% (e.g., no less than 10%,no less than 20%, no less than 30%, no less than 40%, no less than 50%,no less than 60%, no less than 70%, no less than 80%, or no less than90%) of an area 80 between columns 16 of pixels 20, for example area 80between columns 16 within array 12, for example a display areacomprising a convex hull of pixels 20. As illustrated in FIG. 13, atcross section line A, wiring occupies approximately 60% of area 80, atcross section line B wiring occupies approximately 40% of area 80, andat cross section line C wiring occupies approximately 20% of area 80(assuming for this purpose only that the referenced Figures are drawn toscale). In some embodiments, wiring occupies no less than 5% (e.g., noless than 10%, no less than 20%, no less than 30%, no less than 40%, noless than 50%, no less than 60%, no less than 70%, no less than 80%, orno less than 90%) of a display area of flat-panel display 99, forexample a display area comprising a convex hull of pixels 20 in array12. Using larger amounts of the display area for wires (e.g., 40%)improves the conductivity of the wires and can reduce the number ofintegrated circuits on display substrate 10.

Embodiments of the present disclosure are illustrated in the flowdiagrams of FIGS. 14-19. According to some embodiments and referring tothe plan view of FIGS. 1 and 3 and the flow diagram of FIG. 14, a methodof controlling a flat-panel display 99 comprises providing flat-paneldisplay 99 in step 100, providing first column data on first column-dataline 32A to a first column 16 of pixels 20 in a first row group 44A bycolumn controller 30 in step 110 and providing second column data on asecond column-data line 32B to a second column 16 of pixels 20 in asecond row group 44B by column controller 30 in step 120, where thereceiving rows 14 are selected through row-select lines 42, e.g., byrow-controller 40. First column-data line 32A and second column-dataline 32B are different column-data lines 32 and the first column dataand the second column data are provided concurrently and at the sametime. First column 16 of pixels 20 in first row group 44A and secondcolumn 16 of pixels 20 in second row group 44B can be in a common column16 of array 12 of pixels 20. Row controller 40 can then select differentrows 14 in both first and second row groups 44A, 44B and the processrepeats until the entire array 12 of pixels 20 are loaded with data,after which the process begins anew for a second image frame.

According to some embodiments and referring to the plan view of FIGS. 8and 10-12, a method of controlling a flat-panel display 99 comprisesproviding flat-panel display 99 in step 100 and providing a row-selecttoken to a row 14 of pixels 20 in each row group 44 by column controller30 as shown in FIG. 8 (for one row group 44). According to someembodiments and the flow diagram of FIG. 15A, a row-select token isprovided by column controller 30 to a row 14 of pixels 20 in each rowgroup 44 (e.g., to first row group 44A in step 130 and to second rowgroup 44B in step 140) at the same time as shown in FIG. 10, after whichcolumn data can be provided to the selected rows 14 by column controller30 on control-data lines 32A, 32B. The row-select tokens are thenserially passed through columns 16 of pixels in each row group 44 andcolumn data successively provided to each selected row 14.

According to some embodiments and as shown in FIGS. 11 and 12 and theflow diagram of FIG. 15B, a row-select token is provided to a single row14 of pixels 20 in array 12 of pixels 20 by column controller 30, evenwhen array 12 comprises more than one row group 44, and the row-selecttoken is passed from last row 14 of first row group 44A to first row 14of second row group 44B. At the same time, a second row-select token isprovided by column controller 32 to first row 14 of the first row group44A so that a row 14 of pixels 20 in both first and second row groups44A, 44B are simultaneously selected. In any of these cases, once a row14 of pixels 20 has received a row-select token, column-data lines 32can provide column data from column controller 30 to pixels 20 inselected rows 14.

As illustrated in the flow diagram of FIG. 16 and the schematic planview of FIG. 10, according to some embodiments a flat-panel display 99is provided in step 100 and row-select tokens are simultaneouslyprovided to a row 14 of pixels 20 in first and second row groups 44A and44B in steps 130 and 140, respectively. First column data is provided onfirst column-data line 32A to a first column 16 of pixels 20 in firstrow group 44A by column controller 30 in step 110 and second column datais provided on second column-data line 32B to a second column 16 ofpixels 20 in second row group 44B by column controller 30 in step 120.

More generally and as illustrated in FIG. 17 for a flat-panel display99, for example as shown in FIGS. 1, 3, 5, 6 10-12, and corresponding tothe two-row-group 44 case of FIG. 14, in some embodiments, a flat-paneldisplay 99 with N row groups 44 and M rows 14 in each row group 44 isprovided in step 100, a first row 14 in each of the N row groups 44 isselected by row-select lines 42 and provided with column data (e.g.,ranging from the first row 14 of first row group 44A in step 210 to thefirst row 14 of the Nth row group 44 in step 220) through column-datalines 32. Subsequently, successive rows 14 ranging from row 2 to row Min each row group 44 are selected and provided with column data (e.g.,row M of first row group 44A in step 230 to row M of the Nth row group44 in step 240). The loading process is then repeated.

As illustrated in FIG. 18 and with reference to FIG. 10 andcorresponding to the two-row-group 44 case of FIG. 15A, in someembodiments for a flat-panel display 99 with N row groups 44 and M rows14 in each row group 44 provided in step 100, a first row 14 in each ofthe N row groups 44 is provided with a row-select token (e.g., rangingfrom the first row 14 of first row group 44A in step 310 to first row 14of the Nth row group 44 in step 320) through serial connections 60 andthen selected rows 14 of each row group 44 are loaded with column datathrough column-data lines 32. Subsequently, the row-select token isserially passed through serial connections 60 to successive rows 14ranging from row 2 to row M in each row group 44 (e.g., row M of firstrow group 44A in step 330 to row 14M of the Nth row group 44 in step340) and then selected rows 14 of each row group 44 loaded with columndata through column-data lines 32. The row-select token passing and row14 loading process is then repeated within each row group 44.

As illustrated in FIG. 19 and with reference to embodiments shown inFIGS. 11-12 and corresponding to the two-row-group 44 case of FIG. 15Bin which row-select tokens are successively passed through entirecolumns 16 of array 12 of pixels 20 in multiple row groups 44, aflat-panel display 99 with N row groups 44 and M rows 14 in each rowgroup 44 is provided in step 100. In step 310 a row-select token isprovided for each pixel 20 in a first row 14 of array 12 of pixels 20.Column data is also provided on each column-data line 32 to the selectedrow 14. Subsequently, the row-select token is serially passed from firstrow 14 through first row group 44 to row 14M and then through the secondrow group 44 until the row-select token reaches first row 14 of the Nthrow group 44 and then to the Mth row 14 of the Nth row group 44, atwhich point the entire display is loaded. After every row 14 in a rowgroup 44 (e.g., first row group 44A) has received the row-select token,a new row-select token is provided by column controller 30 to first rowgroup 44A so that eventually a row 14 in every row group 44 is selectedat the same time so that column data can be simultaneously loaded intoevery row group 44, thereby reducing the data rate necessary to loadflat-panel display 99 for a given frame rate by a factor equal to thenumber of row groups 44.

Pixels 20 and LEDs 50 can be made in multiple integrated circuitsnon-native to display substrate 10. The multiple integrated circuits canbe micro-elements, for example, micro-transfer printed onto displaysubstrate 10 or onto pixel substrate 22 (e.g., as shown in FIG. 2) andpixel substrate 22 micro-assembled (e.g., micro-transfer printed) ontodisplay substrate 10. The multiple integrated circuits can be small,unpackaged integrated circuits such as unpackaged dies interconnectedwith wires connected to contact pads on the integrated circuits, forexample formed using photolithographic methods and materials. In someembodiments, the integrated circuits are made in or on a semiconductorwafer and have a semiconductor substrate. Display substrate 10 or pixelsubstrate 22, or both, can include glass, resin, polymer, plastic, ormetal. Pixel substrate 22 can be a semiconductor substrate and one ormore of pixel controller 24, pixel memory 26, pixel timing circuit 28,and an LED drive circuit are formed in or on pixel substrate 22 (andthus are native to pixel substrate 22). Semiconductor materials (forexample doped or undoped silicon, GaAs, or GaN) and processes for makingsmall integrated circuits are well known in the integrated circuit arts.Likewise, backplane substrates and means for interconnecting integratedcircuit elements on the backplane are well known in the display andprinted circuit board arts.

Micro-elements, such as LEDs 50 or circuit(s) included in pixels 20, canhave an area of, for example, not more than 50 square microns, not morethan 100 square microns, not more than 500 square microns, or not morethan 1 square mm and can be only a few microns thick, for example, nomore than 5 microns, no more than 10 microns, no more than 20 microns,or no more than 50 microns thick.

In a method according to some embodiments of the present disclosure,integrated circuits are disposed on the display substrate 10 by microtransfer printing. In some methods, integrated circuits (or portionsthereof) or LEDs 50 are disposed on pixel substrate 22 to form aheterogeneous pixel 20 and pixel 20 is disposed on display substrate 10using compound micro-assembly structures and methods, for example asdescribed in U.S. patent application Ser. No. 14/822,868 filed Aug. 10,2015, entitled Compound Micro Assembly Strategies and Devices. However,since pixels 20 can be larger than the integrated circuits includedtherein, in some methods of the present disclosure, pixels 20 aredisposed on display substrate 10 using pick-and-place methods found inthe printed-circuit board industry, for example using vacuum grippers.Pixels 20 can be interconnected on display substrate 10 usingphotolithographic methods and materials or printed circuit board methodsand materials.

In certain embodiments, display substrate 10 includes material, forexample glass or plastic, different from a material in anintegrated-circuit substrate, for example a semiconductor material suchas silicon or GaN. LEDs 50 can be formed separately on separatesemiconductor substrates, assembled onto pixel substrates 22 to formpixels 20 and then the assembled units are located on the surface of thedisplay substrate 10. This arrangement has the advantage that theintegrated circuits or pixels 20 can be separately tested on pixelsubstrate 22 and the pixel modules accepted, repaired, or discardedbefore pixels 20 are located on display substrate 10, thus improvingyields and reducing costs.

In some embodiments of the present disclosure, providing flat-paneldisplay 99, display substrate 10, or pixels 20 can include formingconductive wires (e.g., row-select lines 42 and column-data lines 32) ondisplay substrate 10 or pixel substrate 22 by using photolithographicand display substrate processing techniques, for examplephotolithographic processes employing metal or metal oxide depositionusing evaporation or sputtering, curable resin coatings (e.g. SU8),positive or negative photo-resist coating, radiation (e.g. ultravioletradiation) exposure through a patterned mask, and etching methods toform patterned metal structures, vias, insulating layers, and electricalinterconnections. Inkjet and screen-printing deposition processes andmaterials can be used to form patterned conductors or other electricalelements. The electrical interconnections, or wires, can be fineinterconnections, for example having a width of less than fifty microns,less than twenty microns, less than ten microns, less than five microns,less than two microns, or less than one micron. Such fineinterconnections are useful for interconnecting micro-integratedcircuits, for example as bare dies with contact pads and used with thepixel substrates 22. Alternatively, wires can include one or more crudelithography interconnections having a width from 2 μm to 2 mm, whereineach crude lithography interconnection electrically interconnects pixels20 on display substrate 10. For example, electrical interconnectionsshown in FIG. 9 can be formed with fine interconnections (e.g.,relatively small high-resolution interconnections) while column-datalines 32 and/or row-select lines 42 are formed with crudeinterconnections (e.g., relatively large low-resolutioninterconnections).

In some embodiments, red, green, and blue LEDs 52, 54, 56 (e.g.micro-LEDs 50) are micro transfer printed to pixel substrates 22 ordisplay substrate 10 in one or more transfers and can comprise fracturedor separated tethers as a consequence of micro-transfer printing. For adiscussion of micro-transfer printing techniques that can be used oradapted for use in methods disclosed herein, see U.S. Pat. Nos.8,722,458, 7,622,367 and 8,506,867, each of which is hereby incorporatedby reference in its entirety. The transferred light emitters are theninterconnected, for example with conductive wires and optionallyincluding connection pads and other electrical connection structures, toenable a controller (e.g., column controller 30) to electricallyinteract with light-controlling elements to emit, or otherwise control,light.

In some embodiments of the present disclosure, an array 12 of pixels 20(e.g., as in FIG. 1) can include at least 40,000, 62,500, 100,000,500,000, one million, two million, three million, six million, eightmillion, or thirty-two million display pixels 20, for example for aquarter VGA, VGA, HD, 4K, or 8K display having various pixel densities(e.g., having at least 50, at least 75, at least 100, at least 150, atleast 200, at least 300, or at least 400 pixels per inch (ppi)). In someembodiments of the present disclosure, light emitters in pixels 20 canbe considered integrated circuits, since they are formed in a substrate,for example a wafer substrate, or layer using integrated-circuitprocesses. The substrate or layer need not necessarily be silicon, forexample III-V semiconductor wafers or layers can be used to form lightemitters using integrated-circuit processes and are consideredintegrated circuits (or portions thereof) in the context of thisdisclosure.

Generally, display substrate 10 has two opposing smooth sides suitablefor material deposition, photolithographic processing, or micro-transferprinting of micro-LEDs 50. Display substrate 10 can have a size of aconventional display, for example a rectangle with a diagonal of a fewcentimeters to one or more meters. Display substrate 10 can includepolymer, plastic, resin, polyimide, PEN, PET, metal, metal foil, glass,a semiconductor, or sapphire and have a transparency greater than orequal to 50%, 80%, 90%, or 95% for visible light. In some embodiments ofthe present disclosure, LEDs 50 emit light through display substrate 10.In some embodiments, LEDs 50 emit light in a direction opposite displaysubstrate 10. Display substrate 10 can have a thickness from 5 micronsto 20 mm (e.g., 5 to 10 microns, 10 to 50 microns, 50 to 100 microns,100 to 200 microns, 200 to 500 microns, 500 microns to 0.5 mm, 0.5 to 1mm, 1 mm to 5 mm, 5 mm to 10 mm, or 10 mm to 20 mm). According to someembodiments of the present disclosure, display substrate 10 can includelayers formed on an underlying structure or substrate, for example arigid or flexible glass or plastic substrate.

In some embodiments, display substrate 10 can have a single, connected,contiguous system substrate display area (e.g., a convex hull) includingpixels 20 that each have a functional area. The combined functional areaof pixels 20 or LEDs 50 can be less than or equal to one-quarter of thecontiguous system substrate area. In some embodiments, the combinedfunctional areas of the plurality of pixels 20 is less than or equal toone eighth, one tenth, one twentieth, one fiftieth, one hundredth, onefive-hundredth, one thousandth, one two-thousandth, or oneten-thousandth of the contiguous system substrate area. Thus, remainingarea over display substrate 10 is available for additional column-datalines 32 and serial connections 60 that can cover no less than 5% (e.g.,no less than 10%, 20%, 30%, 40%, 50%, 60% 70%, 80%, or 90%) of the area80 between pixels 20 in the display area.

In some embodiments of the present disclosure, LEDs 50 are inorganicmicro-light-emitting diodes 50 (micro-LEDs 50), for example havinglight-emissive areas of less than 10, 20, 50, or 100 square microns. Insome embodiments, light emitters have physical dimensions that are lessthan 100 μm, for example having at least one of a width from 2 to 50 μm(e.g., 2 to 5 μm, 5 to 10 μm, 10 to 20 μm, or 20 to 50 μm), a lengthfrom 2 to 50 μm (e.g., 2 to 5 μm, 5 to 10 μm, 10 to 20 μm, or 20 to 50μm), and a height from 2 to 50 μm (e.g., 2 to 5 μm, 5 to 10 μm, 10 to 20μm, or 20 to 50 μm). The light emitters can have a size of, for example,one square micron to 500 square microns. Such micro-LEDs 50 have theadvantage of a small light-emissive area compared to their brightness aswell as color purity providing highly saturated display colors and asubstantially Lambertian emission providing a wide viewing angle. Suchsmall light emitters also provide additional space on display substrate10 for additional column-data lines 32 and serial connections 60.

According to various embodiments, flat-panel display 99 can include avariety of designs having a variety of resolutions, light emitter sizes,and displays having a range of display substrate 10 areas.

Pixels 20 of flat-panel display 99 can be arranged in a regular array(e.g., as shown in FIG. 1) or an irregular array on display substrate10.

In some embodiments, LEDs 50 are formed in substrates or on supportsseparate from display substrate 10. For example, LEDs 50 or pixelcontroller 24 are separately formed in a semiconductor wafer. LEDS 50 orpixel controllers 24 are then removed from the wafer and transferred,for example using micro-transfer printing, to display substrate 10 orpixel substrate 22. Such arrangements have the advantage of using acrystalline semiconductor substrate that provides higher-performanceintegrated circuit components than can be made in the amorphous orpolysilicon semiconductor available in thin-film circuits on a largesubstrate such as display substrate 10. Such micro-transferred LEDs 50or pixel controllers 24 can comprise a fractured or separated tether asa consequence of a micro-transfer printing process.

By employing a multi-step transfer or assembly process, increased yieldsare achieved and thus reduced costs for flat-panel displays 99 of thepresent disclosure. Additional details useful in understanding andperforming aspects of the present disclosure are described in U.S.patent application Ser. No. 14/743,981, filed Jun. 18, 2015, entitledMicro Assembled Micro LED Displays and Lighting Elements, the disclosureof which is hereby incorporated by reference herein in its entirety.

As is understood by those skilled in the art, the terms “over”, “under”,“above”, “below”, “beneath”, and “on” are relative terms and can beinterchanged in reference to different orientations of the layers,elements, and substrates included in the present disclosure. Forexample, a first layer on a second layer, in some embodiments means afirst layer directly on and in contact with a second layer. In otherembodiments, a first layer on a second layer can include another layerthere between.

As is also understood by those skilled in the art, the terms “column”and “row”, “horizontal” and “vertical”, and “x” and “y” are arbitrarydesignations that can be interchanged (unless otherwise clear fromcontext).

Throughout the description, where apparatus and systems are described ashaving, including, or comprising specific components, or where processesand methods are described as having, including, or comprising specificsteps, it is contemplated that, additionally, there are apparatus, andsystems of the disclosed technology that consist essentially of, orconsist of, the recited components, and that there are processes andmethods according to the disclosed technology that consist essentiallyof, or consist of, the recited processing steps.

It should be understood that the order of steps or order for performingcertain action is immaterial so long as operability is maintained.Moreover, two or more steps or actions in some circumstances can beconducted simultaneously. The disclosure has been described in detailwith particular express reference to certain embodiments thereof, but itwill be understood that variations and modifications can be effectedwithin the spirit and scope of the following claims.

PARTS LIST

-   A cross section line-   B cross section line-   C cross section line-   L length-   10 display substrate-   12 array-   14 row-   16 column-   18 column-control side-   20 pixel-   22 pixel substrate-   24 pixel controller-   26 pixel memory-   28 pixel timing circuit-   30 column controller-   32 column-data line-   32A first column-data line-   32B second column-data line-   32C third column-data line-   32D fourth column-data line-   40 row controller-   42 row-select line/row-select signal-   44 row group-   44A row group-   44B row group-   44C row group-   44D row group-   46 token-passing circuit-   50 light emitter/light-emitting diode (LED)/micro-light-emitting    diode (micro-LED)-   52 red light-emitting diode-   54 green light-emitting diode-   56 blue light-emitting diode-   60 serial connection-   62 timing signal-   64 clock recovery circuit-   80 area-   99 flat-panel display-   100 provide display step-   110 provide first column data to first column-data line step-   120 provide second column data to second column-data line step-   130 provide token to first row group step-   140 provide token to second row group step-   210 load first row of first row group step-   220 load first row of Nth row group step-   230 load Mth row of first row group step-   240 load Mth row of Nth row group step-   310 load token into first row group step-   320 load token into Nth row group step-   330 shift token to Mth row in first row group step-   340 shift token to Mth row in Nth row group step

What is claimed:
 1. A flat-panel display, comprising: a displaysubstrate; an array of pixels distributed in rows and columns over thedisplay substrate, the array having a column-control side, each of thepixels comprising one or more light-controlling elements; and a columncontroller disposed on the column-control side of the array operable toprovide column data to the pixels in the array through column-data linesand to provide a row-select token to one or more pixels in each of thecolumns of pixels through a serial connection to the one or more pixels,wherein the rows of pixels in the array of pixels are arranged in one ormore row groups, and wherein, for each row group of the one or more rowgroups, each column of pixels in the row group receives column data fromthe column controller through a separate one of the column-data lines,and no pixel of the array of pixels in any other row group receivescolumn data through the separate one of the column-data lines, whereinfor each column of the pixels in each of the one or more row groups,each pixel in the column of the row group is directly serially connectedwith a separate serial connection to a neighboring pixel forming a daisychain in the column of the row group, and each pixel in the array ofpixels comprises a token-passing circuit for passing a row-select tokenthrough each column of serially connected pixels in each of the rowgroups.
 2. The flat-panel display of claim 1, wherein each pixel in thearray comprises one or more inorganic micro-light-emitting-diodes. 3.The flat-panel display of claim 2, wherein each of the one or moreinorganic micro-light-emitting-diodes has a length and a width each nogreater than 200 microns.
 4. The flat-panel display of claim 3, whereinwiring occupies no less than 5% of area between the columns of pixels ona surface of the display substrate on which the pixels are disposed. 5.The flat-panel display of claim 1, wherein each of the pixels comprisesa pixel timing circuit.
 6. The flat-panel display of claim 1, whereinthe number of row groups is greater than two.
 7. The flat-panel displayof claim 1, wherein (i) the column controller provides a row-selecttoken directly to at least one row of pixels in each of the row groupsor (ii) the column controller provides a row-select token directly to atleast one row of pixels in only one of the row groups and the row groupsare serially connected.
 8. The flat-panel display of claim 1, whereineach of the columns of pixels comprises pixels in two or more differentones of the row groups.
 9. The flat-panel display of claim 1, whereineach column of pixels comprises pixels that are electrically connectedto different ones of the column-data lines.
 10. A flat-panel display,comprising: a display substrate; an array of pixels distributed in rowsand columns over the display substrate, each of the pixels comprisingone or more light-controlling elements; and a column controller operableto provide column data to the pixels in the array through column-datalines and to provide a row-select token to one or more pixels in each ofthe columns of pixels through a serial connection to the one or morepixels, wherein, for each row of the rows of pixels in the array, eachpixel in the row is in a column of the array, each pixel in the row iselectrically connected to a separate one of the column-data lines, andthe separate column-data line is electrically connected to less than allof the pixels in the column, wherein for each column of the pixels, eachpixel in the column is directly serially connected with a separateserial connection to a neighboring pixel forming a daisy chain in thecolumn and each pixel in the array of pixels comprises a token-passingcircuit for passing a row-select token through each column of seriallyconnected pixels.
 11. A display, comprising: an array of pixelsdistributed in M rows and N columns, the array having a column-controlside, wherein rows of pixels in the array of pixels form G row groups, Ggreater than one, each of the pixels comprising one or morelight-controlling elements; and a column controller disposed on thecolumn-control side of the array operable to provide column data to thearray of pixels through N×G separate column-data lines and to provide arow-select token to one or more pixels in each of the columns of pixelsthrough a serial connection to the one or more pixels, wherein, for eachcolumn of the pixels, each pixel in the column is directly seriallyconnected with a separate serial connection to a neighboring pixelforming a daisy chain in the column and each pixel in the array ofpixels comprises a token-passing circuit for passing a row-select tokenthrough each column of serially connected pixels.